Record-breaking atom laser to hunt quantum gravity

Beam me up, Einstein. The world’s most powerful atom laser could one day be sent into space to probe the mysteries of general relativity and perhaps offer clues to the long-sought connection between gravity and quantum mechanics.

Atom lasers emit beams of matter instead of photons. This is possible using an ultra-cold gas called a Bose-Einstein condensate, which makes millions of atoms behave like a single wave. Previous work created atom lasers by bottling up the ultra-cold gas using powerful electromagnets.

“It acts like a thermos flask, confining the atoms and keeping them from heating up,” explains Wolf von Klitzing at the Institute of Electronic Structure and Laser in Hellas, Greece. Physicists can then guide a beam of atoms out of the “bottle” using radio waves.

But the radio waves used in the past were relatively weak, limiting the power of atom lasers. Von Klitzing and his team found a way to use stronger radio waves, boosting the flow to 108 atoms per second. That is 16 times as powerful as the previous best atom laser, the team claims.

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Fuzzy laser

Von Klitzing hopes to use such a laser on STE-QUEST, a mission now under consideration at the European Space Agency. The mission’s spacecraft will use a high-precision atom laser to look for the effects of something called loop quantum gravity. Finding such effects could help unite Einstein’s general theory of relativity – our best description of gravity – with the world of tiny particles described by quantum mechanics.

While in orbit, STE-QUEST will fire its atom laser, split it in two, then recombine the beams. General relativity has it that space-time is a smooth fabric, but mathematical theories of quantum gravity say that at very small scales, space-time should be grainy. If these grains exist, the split beams would travel through different sets of them, which would affect the way the laser looks when it is recombined.

“What we expect to find is that the final beam will be fuzzy, de-coherent, unlike what it was before it was split into two,” says Bob Bingham at the Rutherford Appleton Laboratory in Oxfordshire, UK, who is part of STE-QUEST but not on von Klitzing’s team.

STE-QUEST is up against several other proposed missions and must compete for an ESA launch. Although it was not selected during ESA’s latest round of mission evaluations, the project is still very active and will be in the next batch of mission ideas up for consideration, says Gerald Hechenblaikner of international group Airbus Defence and Space, who has been asked by ESA to assess STE-QUEST.